I still maintain that if it hadn’t been for the two-metre tall unicycle, we would never have ended up in jail.

The two-metre tall unicycle was a new addition to the show, cobbled together a few days previously out of pieces of scaffolding and old bike parts. Trico had painted it red with silver splodges, and lovingly christened it Flaca –- "skinny girl." It had a few tumescent lumps where the pieces had been welded together, but other than that looked remarkably professional. Trico was ecstatic.

“Isn’t she beautiful?” he would coo, stroking the unicycle’s silver-blotched body. “She is going to earn us a fortune.”

Trico was my boyfriend at the time –- a charismatic (if somewhat erratic) Mexican juggler and unicyclist. We had met at a party in the north Mexican state of Chihuahua, just as my bank account was running dry and I was preparing, reluctantly, to leave the country.

Despite my shaky Spanish, something in our energies had clicked. Within days, we were inseparable. Within weeks, we were hitchhiking south together towards his home town of San Luis Potosí, and I was getting a fierce crash course in street performance. Within months, my juggling and fire dancing were good enough to earn a living on the road, my Spanish was growing in fluency, and I had no plans to leave Mexico any time soon.

The night of the arrest started like many others for us. We were planning to go to a party later, and were hoping to earn enough money beforehand to enjoy it in style. A friend of mine was visiting -– an Estonian girl named Hele who sometimes drummed to accompany our show. Shortly after dusk, we all trooped down to a busy street intersection. Trico and I had played the spot many times before, but never since the arrival of Flaca.

By then, Trico had not only mastered riding Flaca, but also fire juggling whilst atop her. The effect was electrifying: a slender figure bobbing two metres in the air, illuminated by dancing flames. I danced below him spinning chains tipped with balls of fire, and Hele played a fast syncopated rhythm on her drum. We were attracting quite a lot of attention. As it turned out, rather too much attention.

We had only been playing about 10 minutes when the men arrived. They wore black, and had an air of intimidating officiousness.

“We are from the immigration police of San Luis Potosí. Your passports, please.”

Hele and I glanced nervously at each other. Our passports were back in Trico’s house. And did not, I suddenly thought, contain work visas. It had never occurred to me before to wonder if we might need them.

We were escorted a couple of blocks to the San Luis immigration centre and led through a gate into a compound, while Trico was sent to fetch our passports. When he returned, he was ordered to hand them through the gate and not to enter. The guards flicked through them, and smirked triumphantly at us. No work visas.

“Inside.”

The bureaucratic procedure in the centre seemed to go on for hours, conducted by a toad-like man wedged uncomfortably behind a white table. Finally, our pockets were emptied out, our jewellery and shoelaces removed, and we were led through a heavy door into a cramped antechamber. The guard locked the first door behind us before opening the second and ordering us through.

The space we entered had a concrete floor and walls, and an iron spiral staircase like a fire escape that led up to a concrete balcony. It was partially open to the sky, but with a heavy iron grille over the opening. One bathroom and four cell-like rooms faced onto this space: three onto the bottom level and one onto the balcony. During the night, inmates were locked into these rooms, where they slept on blue mats on the floor, but during the day the doors were opened and they were allowed to mingle. There were about 25 people in there: mostly men, but also a handful of women and two small children. Silence fell as we shuffled in, all eyes on us.

One of a pair of young women was first to break the ice, greeting us and offering commiserations. She laughed incredulously when we told her our story.

“So you’re not trying to get to the States?”

“No.”

“You want to stay in Mexico?”

The two women were Hondurans. They had been caught on the highway to Monterrey when their bus had been stopped in one of the random searches conducted by the immigration police to catch illegal immigrants from Central and South America on their way to the US border. Like most of the other inmates, they were disappointed but resigned to their failure, and already planning strategies for the next attempt.

Hele and I were clearly as far from the usual profile of Mexican detention center inmates as it was possible to get. Even the guards seemed unsure of how to handle our situation. After half an hour in the cells we were removed, locked into an unused office, and left there for two nights.

Three meals were brought a day -– lukewarm stews of gristly meat with stale bread rolls. Our repeated requests to phone our embassies were all denied. We watched the sky lighten and darken through the skylight in the ceiling, and wondered how the hell we were ever going to get out.

The third day was a Monday, and the office space was needed. The guards led us back to the cells. After two days of confinement with only each other’s frustration and paranoia for company, it was a relief to be back with the other inmates. Their stories and varying characters offered a welcome distraction.

There was Juan, a smug young cocaine trafficker from Columbia who accompanied his every movement with a nonchalant flex of his muscles, followed by a furtive look around to check that everyone had noticed and was suitably impressed. And Paco, a gaunt and rather simple Salvadoran who had spent three years working illegally in Mexico to send money to his struggling family, before reporting himself to the immigration police to save himself the cost of a return ticket.

There was even a young man from South Korea, whose only offence was having a misprinted entry stamp in his passport and refusing to pay a bribe.

The story I remember best was of a young Salvadoran named Miguel, who sighed when I asked him how he spoke such good English.

‘I’ve lived in the States for most of my life,” he told us. “I arrived there with my mother when I was still very young. She left El Salvador just after the civil war and managed to get with me all the way to Los Angeles. I never had official papers. Two years ago, I was caught and deported back to El Salvador." He shrugged helplessly. ‘What am I supposed to do in El Salvador? I barely remember living there. In LA I had friends, a girlfriend, a job working with my uncle... my whole life was there. I’ve been trying to get back ever since."

The mother of the two children looked on in silence. She was a stocky, gentle Guatemalan woman of about 35 with huge, round eyes. She spent most of her time washing –- herself, her clothes, her children -– and when there was nothing left to wash a tiny furrow of distress would crinkle her brow and she’d sit, awkward and quivering slightly, until enough time had passed that she felt justified in washing one of them again. Watching her, I felt sure that the most tragic stories in the detention center were the ones that weren’t being told.

Hele and I were released later that day with a fine and a deportation order, to be fulfilled within two weeks. Our subsequent penniless run to the US border at Nuevo Laredo -– at the time just beginning its spiral into the carnage of the drug wars –- was one of the most exasperating of my life, bringing me in closer contact with rifle-toting teenagers and the impenetrable corruption of Mexican bureaucracy than I ever want to come again. But armed with white faces and fortunate passports we were, of course, the lucky ones.

As we shuffled past the border guards over the immense bridge than marks the entrance to Texas, I looked down at the murky waters of the Rio Grande stretching out towards the desert. And I thought of all the people for whom the bridge was not an option –- who, if they ever made it this far, would have to cross the river and the desert on initiative alone.

Whatever the rights and wrongs of the situation, I will never forget that what happened to us was just the shadow of a shadow of what happens to hundreds of other men, women and children every single day.

Catriona's book, "The Urban Circus" (Bradt Travel Guides, paperback) is available from your local bookstore and Amazon.